Steam generator



Patented June 9, 1931 UNITED STATES PATENT OFFICE l HANS GLEICHMANN, F IBEBLIN-SIEMIHWSSTADT, GERMANY, SSIGNOB TO SIEMENS- SCHUCXERTWEBKE GESELLSCHAFT IIT BESCHRANKTEB HAFTUNG, OF SIEMENS- STASDT NEAR BEBLIN,.GERMANY, .L CORPORATION OF GERMANY STEAM GENERATOR M invention relates to steam generators, particularly suitable for carrying out the s0- called- Benson steam generation process.

The process for the generation of working steam ready foruse in an engine or the like known as the Benson process is based upon the principle that the pressure and the temperature in all the stages of the generation process are so regulated that no unsteady separation of steam and water (ebullition) takes place. The high pressures develold hereby do not permit the emplo ment o f oilers with large water spaces. T e Benson steam generator consists of a heated system of pipes to which 1U the water is supplied under pressure. Since very large quant1ties of heat must be applied to the system of pipes in a very short time the design and construction of the generator are very di'erent from those of known boilers. 90 My invention consists of an improved construction of such a steam generator. The generator is fired b pulverized coal or an other suitable fuel a apted to be supplied t ugh nozzles and the necessary combustion air is supplied to the flame in a heated state. Ow-

ing to the preheating of the air uncommonly high temperatures develop which are liable to become a source of danger to the masonry in two regards, viz. firstly by themaso'nry expanding considerably owing to the heat and secondly owing to the danger of its destruction by the heat. The lirst da r is avoided by constructing the furnace c amber as a self-supporting shaft capable of freely expanding in its longitudinal direction when heated. The internal workin of the masonry is therefore not hind by restraining and confining structural elements as is the case in all the hitherto known boilers.

It has been found particularly advantageous not to support the upper closm arch by the shaft or stack but to suspend it-om a structure entirely separate from the shaft.

Whether the arch should be suspended as a unlt or in separate parts is merely a question of practicabllity.

vIn order to provide also for radial e ansion of the brickwork, the bricks may, i desired2 be provided with radial slots towards the side of the maximum curvature so that a 1:4306, and in Germany september-1s. 1925.

'pended from beams or girders which are pushed through the bent-over ends of the tubes. The girders are suspended from a structure which, so far as vertical support is concerned, ,is independent of the shaft and need onl be withdrawn to permit the removal o the individual bundles or nests of tubes from the boiler without the necessity of detaching further holding or supporting elements. The arrangement has the further advantage that the free expansion of the tubes is not interfered with by any means of attachment. v

It has already been mentioned that the brickwork of the furnace chamber is liable to suffer in its structural rigidity owing to the heat intensities developed. This drawback is eliminated according to my invention by arranging all tubes of the steam generator in the radiation chamber and in such a manner that they effectively screen the brickwork from the action of the radiation.

In order to protect the Hoor against the action of direct radiation and hot ashes, thev generator tubes are led near the shaft bottom in loops towards the shaft center, thereby forming a water cooled grate through whlc the combustion products pass. Inv contrast with the hitherto lmown water-cooled granulating grat'es the steam generating `tubes themselves are according to my invention employed for cooling the ashes. Special systems of tubes were hitherto employed for this e furnace is fed with pre-heated combustion air. The preheater is constructively combined withthe steam generator. To prevent a useless radiation of heat towards the outside, the steam generator is enclosed by a shell or jacket through which the combustion air is supplied to the furnace. This outer shell is comparatively thin andonly serves for the guidance of the air current. The air sweeps around the entire outside of the steam generator, absorbs the heat penetrating through-the heater wall and thus forms an effective insulating cover. From the air jacket the air passes into the hea-t exchanging device in which it absorbs the heat still contained in the waste gases. The elliciency of the improved heat exchanging device, which will be more fully described hereafter, resides in the configuration ofthe swept surfaces, which are formed as corrug'ations or zigzag surfaces.

The preheating to the highest temperature takes place in the shaft shell proper which is constructed of hollow moulded bricks through which the air flows. This construction affords a special kind of air supply to the combustion chamber viz, throughthe radial slots'in the bricks which, as described above, simultaneously serve for compensating stresses, the air passing radially between the boiler tubes. In this manner not only an intimate mixture of the air with the fuel is attained, but simultaneously a good cooling action by which the brickwork is effectively pro- -tected.

In the drawings affixed hereto Fig. 1 shows a longitudinal section Fig. 2 a partial 'cross-section along line y af-a of Fig. 1.

Fig. 3 a perspective view ofa brick used i in the shaft construction, and

Fi 4 an enlarged section on the line a-a in Fig. 1 through asuperheater chamber, showing the details of the tube suspension.

Like numerals-of reference indicate like parts in all figures of the drawings.

Referring to the drawings 1 is the shaft of the furnace constructed ofhollow moulded bricks which extend to the vicinity of the top.

' It is thus able to expand freely in an axial direction. By reason of the radial slots 40 in each brick, as shownin detail in Fig. 3, the tangential stresses, set up in the shaft when its inner surface becomes hotter than its outer surface, are relieved.` The arch 2 at the top of the shaft is suspended from an iron structure 4 which is entirely separate from the shaft proper. 5 are the steam generator tubes which, as particularly clearly shown in Fig. 2, are all located in the radiation space'6. The superheater tubes 7 are located in the flues 8 swept by the waste gases. The manner of suspending the superheater tubes is clearly illustrated in Fig. 4. The bundles or nests of tubes are suspended from circumferentially disposed girders 19 which rest upon radially disposed girders 20. The girders 19 are bolted togetherby spacing brackets 19a and the -whole tube nest or section can be drawn together out of the chamber, in case of required most completely against the hot flames and i gases. At their lower end 16 the generator tubesare drawn in towards the center of the shaft and form in this way a kind of grate,

as particularly clearly shown in Flg. 2,'

through the spaces of which drop the ashes.

The air of combustion Hows 'through the hollow space 9 Lbetween the thin outer. shell 10 and the preheater chamber proper 11 in the direction of the arrows shown. rom space 9 the air passes into heat exchanging chamber 11 in the direction of the curved arrows. 'In Fig. 2 it will be seen that zigzagshaped sheet-iron walls 14 are located in the heater chamber 11. One side of these sheets is swept by the combustion gases, indicated by dotted arrows, and Von the other by the combustion air to be heated, indicated by full line arrows. -The as and the air flow in opposite directions. ery large heat exchange surfaces may in this way be housed in comparatively small chambers.

In the cross-section of the steam generator the spaces traversed by air are indicated by dashes and the waste gas flues by dots. In flowing through the passage 9 the air first carries along the heat penetrating the wall 16 not be tightly sealed against the walls 16 and 17, which is a substantial advantage of the construction.

From the top ofthe preheater 11 the air flows across the top of the heating chamber 8 (throughducts not shown in detail) into the in Figures 1 and 2, whence part of it flows through radial openings (see 41 in Fig. 3) in the direction of the arrows shown in Figure 1 radially ybetween the generator tubes. The remainder of the air passes down through the dotted ports 24 into ring channel 22, whence it is supplied through ports 23 and central nozzle 13 into the'flame in the combustion chamber. The fuel, for instance gas or powdered coal, may be supplied through pipe 25 to nozzle 13. Combustion air is supplied thus to the llamel from all sides, whereby brickwork 1 is simultaneously cooled. The combustion gases flow eventually downward through the tube grid 5leaving the chamber through openings 27 and,passing through ducts 26, .enter the chamber 8 wherein they travel upwards past heating tubes 7. Thence they pass through openings 28 vin wall 17 and traverse the preheater cha'nbers 11 in a downward direction, escaping nally through the flue 12 intothe stack. j y

As already pointedout ythe arch of the shaft is not carried by the shaft itself, but by an iron structure 3 and 4 entirely separate Vhollow bricks 1 in the direction of the arrows 'the generator. for operating and controlling the generator from the shaft. In conjunction herewith and owing to the whole designv of the steam generator proper particularly economical possibilities of construction result, insofar as such a generator may be erected without a boiler house in the open air, and the girder structure for supporting the generator tubes may simultaneously be designed as a roof for In such a case all apparatus would be contained for instance within the engine house, not lshown here.

Various changes and modifications in the details of my invention may be made within the scope of my claims without departing from the spirit of my invention.

I claim as my invention 1. A. steam generator having a nozzle lfurnace, heat absorbing tubes disposed in the furnace, a self-supporting furnace shaft and further heat absorbing elements disposed to absorb heat from the furnace gases after they have left the furnace, said shaft being hollow for conducting the combustion air to the furnace, said heat absorbing tubes being disposed in the furnace tofshield the shaft walls against the hot gases, said shaft, said 4heat absorbing tubes, and said heat absorbing elements being disposed concentrically with each other, and a casing surrounding said heat` absorbing elements and a plurality of partitions between said casing and said shaft, vertically supported independently of said shaft and dividing the space between the casing and the shaft int a plurality of chambers in which lsaid absorbing elements are sectionally disposed, said partition walls having radially extending glrders serving as a support for said heat absorbing elements.

2. A steam generator having a furnace shaft and an air nozzle concentrically disposed with said shaft, heat absorbing tubes disposed to absorb heat from the combustion gases, said shaft having a hollow wall Jfor conducting combustion air, an air chamber surrounding said nozzle, a-plurality of ducts leading from said hollow wall portion to said chamber, and a plurality of radial air supply combustion gases passing from the combus tion chamber through said jacket and said air preheater in series for effecting a heat exj as change between the gases, the superheater tubes and the combustion air, said. jacket being radially divided into a plurality of compartments, each containing a removably suspended group of superheater tubes.

4. A steam generator having a nozzle furnace, in combination with a furnace shaft, 'an outlet near the-bottom of said shaft, heat absorbing tubes disposed adjacent to the in,

terior wall of said shaft, said tubes forming loops extending inwardly near the outlet of the .shaft and across the path of the gases passing through said\outlet, and serving as a screen through which all. of the products of combustion must pass on their way to the furnace stack. Y

' In testimony whereof I affix my signature.

HANS GLEICHMANN.

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